The present invention relates to the general field of footwear accessories and is particularly concerned with a weighted footwear insert.
The efficiency of weights for improving muscle strength and tone is well established. Athletes in particular, for example, have long been training with weights mounted on the lower limbs in order to develop muscles for running, jumping and the like. Non-athletes can also benefit from such training aids by merely incorporating the use of the training aids in their daily regimens of moving about. Repeated use of such lower limb mounted weights when active can lead to strengthening of the leg muscles, increase in cardiovascular capacity and a generally higher metabolic rate. It is also believed that rehabilitative efforts might be hastened and improved with specific training of locally mounted weights.
The prior art is replete with various types of structures for adding weight to the lower limbs of intended users. One particularly popular method of adding weight to the lower limbs makes use of conventional ankle weights, including a strap configured and sized for mounting around the ankles, and having weights attached thereto. Apart from being most uncomfortable, one of the drawbacks associated with conventional ankle weights is that the ankle takes too much shock with each step or stride when the weight is placed around the ankle, as the ankle itself is what stops the mass of the weight from accelerating to the ground with each step. This causes the weight to jam the ankle with each step, leading to stretched ligaments and sore tendons after several weeks of use.
The intended mass needs to be below the foot if the body is to be prevented from decelerating the mass with each step. If the mass is below the foot, the ground the foot is striking stops the mass instead, eliminating shock to the body.
The solution to eliminating shock from weight placed above the ankle is to attach or incorporate the weight to the footwear. This solution has been recognised in the prior art. Indeed, some prior art patents disclose footwear incorporating weighted elements. For example, U.S. Pat. No. 4,458,433 issued Jul. 10, 1984 and naming Frank Stempski as inventor discloses a footwear having a weight pocket at the outside of a toe region of the upper structure for receiving removable weights therein. The structure also proposes optional heel and side pockets for additional weights. The structure disclosed in U.S. Pat. No. 4,448,432 however has major flaws including that positioning of the weight above the sole of the foot tends to create awkward muscle development. The disclosed structure also makes it difficult to prevent the weighted mass from moving around under heavy accelerations.
U.S. Pat. No. 5,231,776 issued Aug. 3, 1993 naming Rodger D. Wagner as inventor discloses a footwear incorporating a grid matrix which is moulded into the footwear and sandwiched between the inner and outer sole of the latter. Relatively small weighted spheres typically of less than 1 mm of diameter are inserted into the lattice grid matrix. Although presenting a somewhat elegant solution to the problem of weight distribution, the structure disclosed in the U.S. Pat. No. 5,231,776 suffers from the fact that the weight is permanently fixed into the shoe. The structure thus lacks in versatility and transferability between shoes.
U.S. Pat. No. 3,517,928 discloses a weighted shoe using a weight receiving member frame inside the shoe, the weight receiving member frame being coextensive with the sole. The weight-receiving frame is permanently built into the shoe and has openings for receiving different weight plugs. One of the main disadvantages associated with this device is that a favourite or expensive shoe would need to be permanently altered to properly incorporate the member frame according to the disclosure.
U.S. Pat. No. 4,252,315 issued Feb. 24, 1981 naming Akira Kimura as inventor discloses a training aid including a toe portion and a heel portion with both having a core member made of heavy metal and a resilient covering member surrounding the core member. The toe and heel portions are so shaped that they form substantially a sole configuration when they are placed side by side on the sole of a shoe.
One of the main drawbacks associated with the structure disclosed in U.S. Pat. No. 4,252,315 relates to the lack of flexibility of the core members which leads to discomfort and potential injury to the wearer since the core members are unable to conform to the wearer""s foot contour especially during motion.
The problem of weighted insoles having insufficient flexibility and being unable to conform to the changing configuration of a foot during motion has been recognized in the prior art. Attempts have been made to at least partially solve the problem. For example, U.S. Pat. No. 4,709,921 naming Antonette G. Valuikas and Ralph Valuikas as inventors and issued Dec. 1, 1987, as well as U.S. Pat. No. 5,638,613 naming James H. Williams and issued Jun. 17, 1997, both specifically address the lack of flexibility issue.
U.S. Pat. 4,709,921 discloses a weighted shoe insert having a weighted base member formed either as an integral portion of a shoe, or as a discrete insert sandwiched between an upper adhesively backed cover and a lower adhesively backed cover. The base member contains a series of perforation and edge contours which facilitate the shaping of the base member to conform with the shape of a human foot. In a second preferred embodiment, the base member is composed of a series of discrete elements in which chafing between adjacent segments has been substantially reduced by the contouring of the edges.
U.S. Pat. No. 5,638,613 discloses a weighted insole having a pair of flat weights encapsulated inside a flexible material, which is formed into an insole for placement in a shoe. A first weight is encapsulated in front and a second weight is encapsulated behind the ball of the foot area. The second weight additionally has cutouts at the arch and heel areas of the foot.
These unweighted areas throughout their thicknesses include insole materials that provide extra comfort and cushioning where the user typically places more weight on the foot. The front and back weighted construction additionally allows for flexibility of the insole at the ball area. A pattern of nodes is projected from the bottom of the insole to frictionally hold the insole in place in the shoe.
Although U.S. Pat. Nos. 4,252,315, 4,709,921 and 5,638,613 recognize the need for a flexible sole they still disclose structures presenting inherent major drawbacks that are not taking into account the relative complexity of the human foot and the knowledge emanating from the field of advanced athlete training and rehabilitation. In order to fully understand the problems associated with prior art structures and the advantages associated with the present invention a basic knowledge of foot anatomy is required.
The foot and ankle combine flexibility with stability because of the many bones they comprise and because of their shapes. The lower leg, ankle and foot have two principle functions, mainly propulsion and support. For propulsion, they act like a flexible lever. For support, they act like a rigid structure that holds up the entire body. The foot performs several important functions such as acting as a support base that provides the necessary stability for upright posture with minimal muscle effort, providing a mechanism for rotation of the tibia and fibula during the stance phase of gait, providing flexibility to adapt to uneven terrain, providing flexibility for absorption of shock by becoming a rigid structure in the pronated position and acting as a lever during xe2x80x9cpush-offxe2x80x9d.
The joints of the lower leg, ankle and foot act as functional groups not as isolated joints. The movement occurring at each individual joint is minimal. However, when combined, there normally is sufficient range of motion in all of the joints to allow functional mobility as well as functional stability. A suitable insole structure thus must take into account the movements occurring at each individual joint, however minimal. In particular, a suitable insole structure must take into account the movements occurring at each individual joint not only the movements leading to a flexing of the foot about a generally transversally oriented pivotal axis but also at the joints leading to flexing of the foot about a generally longitudinal pivotal axis orientation or a combination of both longitudinal and transversal orientation.
For ease of understanding, the joints of the foot are divided into three sections namely hind-foot or tarsus, the mid-foot or mid-tarsus, and the forefoot or metatarsus. The hind-foot contains two bones, the talus and the calcaneus. The joints of the hind-foot are the tibiofibular joints. The interior or distal tibiofibular joint is a fibrous or syndesmosis type of joint. The movements at this joint are minimal but allow a small amount of spread at the ankle joint during dorsiflexion.
The talocrural joint, or ankle joint, is a uniaxial, modified hinge synovial joint located between the talus, the medial malleolus of the tibia and the lateral malleolus of the fibula. The talocrural joint is designed for stability, not mobility. The subtalar joint is a synovial joint having three degrees of freedom and a closed pack position of supination. The movements possible at the subtalar joints are gliding and rotation. In addition, medial rotation of the leg causes a valgus, or outward movement of the calcaneus. Lateral rotation of the leg produces a varus or inward movement of the calcaneus.
The mid-tarsal joints part of the mid-foot include the talocalcaneonavicular joint, typically a ball and socket and synovial joint with three degrees of freedom. Movements possible at this joint are gliding and rotation. The cuneonavicular joint is a plain synovial joint. The movements possible at this joint are sliding and rotation. The cuboideonavicular joint is fibrous. The movements possible at this joint are gliding and rotation.
The intercuneiform joints are plain synovial joints. The movements possible at these joints are slight gliding and rotation. The cuneocuboid joint is a plain synovial joint. The movements of slight gliding and rotation are possible at this joint. The calcaneocuboid joint is a saddle shape with a closed pack position of supination. The movement possible at this joint is gliding with conjunct rotation. The mid-foot contains the three cuneiforms, the navicular and the cuboid and is separated from the hind-foot by the transverse mid-tarsal joint of Chopart.
The forefoot contains the five metatarsals and fourteen phalanges. It is separated from the midfoot by the tarsometatarsal joint of Lisfranc. Joints of the forefoot include the torsometatarsal joints which are plain synovial joints offering possible gliding movement. They also include four intermetatarsal joints which are plain synovial joints offering the possibility of gliding motion. They further include five metatarsophalangeal joints that are condyloid synovial joints with two degrees of freedom. The movements possible at these joints are flexion, extension, abduction and adduction. The joints of the forefoot further include interphalangeal joints, which are synovial hinged joints with one degree of freedom. The movements possible at these joints are flexion and extension.
The structures disclosed in the prior art patents fail to properly account for the possible movements of the numerous joints of the human foot necessary to allow for the proper biomechanical functioning fit. For example, both U.S. Pat. Nos. 4,252,315 and 5,638,613 assume that the mid and hind-foot are mostly static and that a relatively solid piece of material supporting both the mid and hind-foot will provide adequate support during motion. U.S. Pat. No. 5,638,613 discloses the use of a material allowing for semi-permanent forming in order to take into consideration the particular initial configuration of a static foot. However, it doesn""t take into account that the sole of the foot is constantly changing in configuration during motion. The proposed semi-permanent design does not adapt to the foot""s necessary freedom of movement and continual configuration change necessary for dynamic action found in athletic activity.
The typical foot active movements include plantar flexion of the ankle. During plantar flexion the heel of the foot will normally invert when the movement is performed when in weight bearing position. If heel inversion does not occur, the foot will be unstable. Dorsiflexion of the ankle or standing on the heels is usually 20 degrees past the anatomic position or when the foot is approximately at 90 degrees to bones of the leg. Supination or standing on the lateral edge of the foot and pronation or standing on the medial edge of the foot are respectively through ranges of 45 to 60 degrees and 15 to 30 degrees although there is variability among individuals. Supination or inward torsion combines the movements inversion, adduction and plantar flexion. Pronation or outward torsion combines the movements of eversion, abduction and dorsiflexion of the foot and ankle. The prior art patents fail to disclose structures allowing for the complete range of possible movements. For example, the lack of lateral flexibility renders both pronation and supination virtually impossible.
In normal stance, the body weight is equally distributed between the heel and ball of the foot. Muscular contraction is necessary to maintain this normal balance. For example, with muscle relaxation, 80 percent of the weight loaded on the knee will be distributed onto the metatarsal and 20 percent on the calcaneus. In normal stance, the contraction of the triceps surae creates an equal weight distribution between the metatarsal and the calcaneus.
Weight distribution among the metatarsal also depends on muscle contraction. In normal stance, the one half body weight borne by the metatarsals is distributed in the ratio 2:1:1:1:1 from the medial to the lateral rays. That is, the first metatarsal bears twice the weight of any of the others and one third of the weight carried by the forefoot or one sixth of the body weight. Studies have shown that relatively small changes in muscle balance and tone can result in significant changes in the load distribution of the foot. Therefore, the load mechanism in the foot is far more than an aesthetic arch. It depends on normal function of the bones, ligaments and muscles acting in concert.
Another factor affecting weight distribution is the direction of thrust of the tibia in standing and especially in walking and running. Torque on the tibia has significant effect on loading. Internal torsion produces pronation and loads the first ray, while external tibial torsion produces supination and loads the lateral rays. These loads, however, can be negated if muscles are contracted during loading. In walking, the weight is shifted from the heel to the ball of the foot in a straight line that parallels the line of forward progression. In a normal out-toeing gait, the weight moves from the lateral calcaneus and heel in a straight line forward to the head of the first metatarsal. In an ingoing gait, the heel strikes on the inner border of the heel and the weight moves towards the lateral metatarsal.
The structures disclosed in the prior art patents do not take into consideration the complexity of the movements of the various joints and, hence, the changes in the weight distribution during motion. The use of a material providing semi-permanent forming as proposed by the U.S. Pat. No. 5,638,613 and the use of an insole having only transversal perforations or transversally separated discrete elements as proposed by U.S. Pat. No. 4,709,921 simply do not account for variations in position and weight distribution occurring in the transversal direction during movement of the foot.
Furthermore, the prior art structure, by failing to take into consideration the transversally occurring phenomena, also failed to take into consideration the crucial role of the longitudinal arches of the foot for weight bearing. The arches of the foot are maintained by three mechanisms: wedging of the interlocking tarsal and metatarsal bones takes place; the ligaments on the plantar aspect of the foot play a significant role; and the intrinsic and extrinsic muscles of the foot and their tendons help to support the arches.
The longitudinal arches form a cone as a result of the angle formed by the metatarsal bones with the floor. The medial longitudinal arch being more evident, this angle is greater on the medial side. The specific cone shaped configuration of the longitudinal arches simply cannot be matched by the structures proposed in the prior art patents and, hence, the proper arch support results from these structures.
The medial longitudinal arch consists of the calcaneal tuborisity, the taleas and the nevicular bone, three cuneiforms and first, second and third metatarsal bones. The calcaneus, cuboid forth and fifth metatarsal bones make up the lateral longitudinal arch. The transverse arch consists of the navicular bone, cuneiforms and cuboid and metatarsal bones. The arch is sometimes divided into three parts, tarsal, posterior metatarsal and interior metatarsal. The loss of the interior metatarsal arch results in callous formation under the heads of the metatarsal bones. The metatarsal joints are slightly extended when the intended user is in the normal standing position because the longitudinal arches of the foot curve downward towards the toes. Normal arches of the foot hence play a crucial role for functional stability and mobility. Improper support of the arches may potentially lead to injury.
The fact that the prior art structures are not adapted to follow the changing contour of the sole of the feet in motion and to provide adequate arch support not only potentially leads to improper muscle development and potential injury, but it also actually leads to erroneous central nervous system adaptation which, in turn, may be detrimental to the performance of the athlete. Indeed, it has been shown that repeated training of specific biomechanical motions allows the establishment of motor memory between the brain and individual muscle cells through the central nervous system.
Unrelated motor activity associated with training muscles in matters that do not use the same biomechanical motion as used in competition can confuse the ability of the brain to establish the motor memory pathways necessary for the execution of specific athletic activities. One of the objectives of modern training is thus to train the brain and body to strengthen and learn a specific action in the least amount of time, with a minimum of other athletic activity which uses the brain and central nervous system in a different matter and which would potentially cause the brain to develop unrelated motor memory pathways.
In addition the biomechanical action of the muscle groups, the development of chemical energy generated by the cells of the muscle groups being used must also be considered. The rate of generation of chemical energy will differ with different levels of expenditure. Full speed activity uses exponentially more power than half or quarter speed activity. Individual muscle cells adapt only to the power level being repeatedly trained.
Prior art structures are not well adapted to establishing proper motor memory pathways, since the lack of flexibility on the proposed weighted plate forces the subject to use different biomechanical parameters during training as compared to those used during actual competition, or other specific activities without the plates. The use of training equipment which forces the subject to alter normal motor memory and biomechanical sequences also impedes the ability of individual muscle cells to fully develop energy output for competition, or other specifically intended uses.
The full development of an individual cell""s maximum energy output is only possible if the cell is consistently being used or trained in the correct motor memory sequence. Training individual muscle cells in a different manner has been shown to primarily develop the cells for that particular motor sequence only. Transfer of such neuromuscular conditioning to other motor actions has been shown to be less than optimal. This is why modern sport training techniques have become very motor specific to the training task at hand.
Another drawback associated with prior art structures is that since the prior art insoles are made out of relatively large segments attached to each other, the pressure exerted by the foot of the intended user is not transmitted proportionally to corresponding areas of the shoe structure but rather partially absorbed and redistributed to the insole itself, which has no shock absorbing capability as compared to the midsole of modern training footwear, significantly altering and reducing the shock absorption properties of said footwear. This, in turn, reduces the overall bio-mechanical efficiency of the shoe-insole combination.
Other drawbacks associated with prior art structures are related to these specific types of materials and overall configurations that have been selected. Indeed, the structures disclosed in U.S. Pat. Nos. 4,709,921 and 5,638,613 are made of lead, a toxic material, which can potentially be absorbed by the human skin especially in the often hot and humid environment of a shoe during training.
Furthermore, the structures disclosed in U.S. Pat. Nos. 4,709,921 and 5,638,613 are relatively thick as compared with the structure of the proposed invention. When these relatively thick insoles are put in shoes that come with conventional modern insole liners, which are quite thin, they take up a relatively large volume, forcing the user to buy an extra pair of shoes to train. Indeed, most impact absorption in modern training shoes is provided by the advanced materials now found in the mid-soles of such footwear and not the insole itself. The modern insole that cover the stitching in the shoes upper construction is often very thin and differs in thickness and overall function from one shoe design to another. The relatively thick insoles proposed by U.S. Pat. Nos. 4,709,921 and 5,638,613 are proportionally relatively thick relative to the insoles of modern footwear.
Accordingly, there exists a need for an improved weighted footwear insert. Advantages of the present invention include that the proposed weighted footwear insert is specifically designed so as to follow the changing configuration of the sole of the feet of an intended user during motion.
The proposed weighted footwear insert is designed so as to take into account variations in configuration and weight distribution of a given foot sole section in a transversal direction. The improved flexibility of the proposed weighted footwear insert allows the latter to instantly and fully adapt to the mid-sole below and the insole above of the conventional shoe, thereby allowing full transfer of the footwear""s cushioning properties.
The proposed weighted footwear insert allows for adequate support of the foot arches while providing flexibility thus reducing risk of injury during training.
Furthermore, the proposed weighted footwear insert allows for the development of optimized motor memory pathways during training. The proposed weighted footwear insert is configured so as to be easily transferable between pieces of footwear thus reducing the need for buying multiple inserts.
Furthermore, the proposed weighted footwear insert is designed as to be comfortable and easily concealed within conventional footwear so as not to deter to the overall aesthetical aspect of the latter. Furthermore, the proposed weighted footwear insert has a generally thin configuration so as to obliviate the need for buying a shoe of a larger size in order to incorporate the weighted footwear insert in accordance with the invention.
Still further, the proposed weighted footwear insert is specifically designed so as to transmit the pressure exerted by the foot of the intended user directly to the shoe structure with reduced alteration of the pressure distribution on the shoe structure so as to maintain the overall biomechanical efficiency of the shoe-insole combination.
The present invention also relates to a method for forming a weighted footwear insert in accordance with the present invention. The proposed method allows for reformation of a weighted footwear insert through a set of optimized steps that can be performed with conventional equipment and using conventional materials so as to allow for the production of a weighted footwear insert that will be economical, long lasting and relatively trouble free in operation. The proposed method also allows for the production of customized weighted footwear inserts that are optimized for specific individual biomechanical parameters and training techniques.
In accordance with an embodiment of the present invention, there is provided a weighted footwear insert for use inside a footwear, the footwear being wearable by a foot of an intended user, the foot having a foot sole, the footwear including a generally elongated insole, the insole defining an insole peripheral edge, an insole longitudinal axis and an insole transversal axis, the footwear insert comprising: a weighted plate, the weighted plate defining a plate first surface, a plate second surface, a plate toe end, a plate heel end, a plate peripheral edge, a plate longitudinal axis and a plate transversal axis, the weighted plate being configured and sized for insertion into the footwear with the plate longitudinal axis extending in a direction generally parallel to the insole longitudinal axis and the plate transversal axis extending in a direction generally parallel to the insole transversal axis; the weighted plate defining a first pair of plate segments, the plate segments defining a segment longitudinal fold line therebetween for allowing the plate segments to fold relative to one another about the segment longitudinal fold line; the segment longitudinal fold line defining a longitudinal fold line orientation axis, the longitudinal fold line orientation axis defining a longitudinal fold line-to-longitudinal axis angle between the longitudinal fold line orientation axis and the plate longitudinal axis, the longitudinal fold line orientation axis defining a longitudinal fold line-to-transversal axis angle between the longitudinal fold line orientation axis and the plate transversal axis; the longitudinal fold line-to-longitudinal axis angle being smaller in value then the longitudinal fold line-to-transversal axis angle; the weighted plate also including a generally transversally extending transversal bending means for allowing the weighted plate to bend along the transversal bending; whereby the longitudinal segment fold line extends in a more longitudinal then transversal direction for allowing the weighted plate to substantially follow the transversal contour of the foot sole.
Preferably, the transversal bending means includes a segment transversal fold line extending between the first pair of plate segments and a second pair of plate segments, both the first and the second pair of plate segments having their respective plate segments separated by the segment longitudinal fold line. Preferably, the transversal bending means includes a plurality of segment transversal fold lines.
Conveniently, the plate segments are disposed relative to each other so as to define a segment spacing therebetween; the weighted footwear insert further comprising a flexible coupling means attached to adjacent plate segments for flexibly coupling adjacent plate segments together so as to allow bending therebetween about the coupling means.
In one embodiment, the flexible coupling means includes a first flexible membrane fixed to the plate first surface on adjacent plate segments, the first flexible membrane extending across the segment spacing. Preferably, the flexible coupling means also includes a second flexible membrane fixed to the plate second surface on adjacent plate segments, the second flexible membrane also extending across the segment spacing. In another embodiment, the flexible coupling means includes a flexible web of material extending integrally between adjacent plate segments.
Optionally, the coupling means allows bending between the plate segments within a predetermined limited bending range. Optionally, the first pair of plate segment is made of plate segments having different densities. Optionally, the first pair of plate segments is made of plate segments having different cross-sectional configurations. Optionally, the segment longitudinal fold line extends across the weighted plate from the plate toe end to the plate heel end.
In accordance with one embodiment of the invention, the weighted footwear insert defines a main segment longitudinal fold line and a pair of auxiliary longitudinal fold lines, the main segment longitudinal fold line extending substantially longitudinally across the weighted plate and being substantially centrally positioned relative to the plate peripheral edges, the auxiliary longitudinal fold lines being positioned on each side of the main longitudinal fold line and following a direction so as to be in a generally central position between the main longitudinal fold line and an adjacent plate peripheral edge.
In accordance with another embodiment of the invention the weighted insert includes a main segment longitudinal fold line and a set of auxiliary longitudinal fold lines, the main segment longitudinal fold line extending substantially longitudinally across the weighted plate and being substantially centrally positioned relative to the plate peripheral edges, the auxiliary longitudinal fold lines being positioned on each side of the main longitudinal fold line between the main longitudinal fold line and an adjacent plate peripheral edge, the auxiliary fold lines extending from the plate toe end to a position intermediate to the plate toe and heel ends, the weighted footwear insert also including a plurality of segment transversal fold lines and a generally xe2x80x9cUxe2x80x9d-shaped fold line positioned adjacent the plate heel end.
Optionally, the weighted insert includes a plate aperture extending through the plate, the plate aperture being filled by a generally resilient material.
In accordance with the present invention there is also provided a weighted footwear insert for use inside a footwear, the footwear being wearable by a foot of an intended user, the foot having a foot sole, the weighted footwear insert comprising: a weighted plate, the weighted plate defining at least one generally longitudinally oriented longitudinal fold line and a set of generally transversally oriented transversal fold lines for allowing the weighted plate to fold according to the configuration of the foot sole and to follow the changes in configuration of the foot sole during movement of the foot.
The present invention also relates to a method of forming a weighted footwear insert comprising the steps of cutting a blank having substantially the planform of an insole into a relatively thin piece of generally dense material; forming at least one generally longitudinally oriented longitudinal fold line and a set of generally transversally oriented transversal fold lines in the blank.
Preferably, the method further comprises the step of determining an optimized blank configuration and fold line pattern for the foot taking into consideration the physiological characteristics of the foot prior to cutting the blank and the longitudinal and transversal fold lines according to the optimized blank configuration and fold line pattern.